1. Field of the Invention
This invention relates to electric clamping elements and more particularly to insulation slitting or piercing contact clamps.
2. Prior Art
This invention is directed to that type of electrical contact clamping element which engages the conductor core of an electrical wire surrounded by an insulation jacket without requiring stripping of the jacket.
Particularly this invention is directed to that type of clamping element that has two adjacent clamping slots open to a common end of the element and defined by bar members. Such clamping elements must of course have a construction giving proper electrical contact. In addition they must also have a sufficiently large spring force to insure that the insulation jacket is pierced or slit completely through to the conductive wire core when the insulated wire is pressed into the clamping slot.
The prior art has attempted to meet these two basic requirements in one construction by creating the element out of two parts formed of different materials. In such a construction one of the parts, which may form the center post or the central bar will be formed of a particularly good electrical conductor material such as, for example, nickel silver. The other part forms the exterior bars. These are separated from one another by the center post and wire clamping slots are defined between the exterior bars and the center post. This other part may be formed of a material exhibiting desired resilient properties. Such a resilient material may, for example, be beryllium. The two separate parts are then properly positioned with respect to one another and are thereafter connected by means such as spot welding.
The aforementioned type of known clamping element is deficient in that because of the usage of different materials and the resultant assembly and connection production steps, the resultant element is expensive.
To reduce expense, it has been known to form the element from a strip of material which is punched to define spaced clamping slots. The material is chosen for the desired electrical conductivity. In this type of single piece construction, due to the resilient deficiency of the good conductor materials, the element can only be used a few times. That is to say that repeated insertion of insulated wires into the slot will overstretch the exterior bars to the extent that their spring tension will be insufficient to properly pierce the insulation of subsequently inserted wires. This type of element can thereafter only be properly used in connection with a tool which spans the exterior bars during wire clamping. An additional deficiency of such prior constructions is the fact that they are usable only with insulated wires having a conductive core of one size or, when using subsequently clamped wires, the element can be used only with insulated wires having increasing conductor core diameters. It is only in these instances that the element can assure a reliable electric contact.
It would therefore be an improvement in the art to provide a single material double slot electrical contact element which provides sufficient spring strength to insure proper installation piercing while allowing usage with conductor cores of differing diameters without the necessity of using a tool during the clamping process.